Charter for Working Group

The Calendaring Extensions working group is chartered to developextensions to the iCalendar (RFC 5545), iTIP (RFC 5546), andCalDAV (RFC 4791) standards.

This working group will do the following:

- Develop an extension to iCalendar to support non-Gregorian recurrencerules, without the need to support new calendar scale values iniCalendar as a whole. This will allow for easy implementation of theprimary use case for non-Gregorian support in calendar systems, withoutthe need for significant changes to the iCalendar format. Thenon-Gregorian calendar system should be based on the InternationalComponents for Unicode work by the Unicode Consortium(http://site.icu-project.org).

- Develop an extension to iCalendar to support a new component type thatallows users to express arbitrary, possibly repeating, periods of"available" time. The primary use case for this is for users to expresstheir "office hours" (e.g., Monday-Friday, 9am-5pm) in a standard way toensure free busy lookups show the correct periods of availability.

- Define a set of new iCalendar properties and parameters to standardisesome existing experimental X- properties in common use, based on asurvey of existing implementations.

- Define a set of new iCalendar properties and parameters to cover keyuses cases that implementers have identified, including, but notlimited to, a new "IMAGE" property (to allow embedding/linking ofimages tied to a specific event), and a "CONFERENCE" property (to allowembedding information about dial-in numbers and similar multi-partycommunication options for an event).

The working group will work under the following parameters:

- The extensions developed are expected to be backwards-compatible withthe existing calendar standards. Incompatibilities must be identified,minimized, and justified.

- For each set of extensions, examine their impact on the iTIP protocol(RFC 5546), and define any necessary extensions to iTIP to accommodatesuch impact.

- For each set of extensions, examine their impact on the CalDAVprotocol (RFC 4791), and define any necessary extensions to CalDAV toaccommodate such impact. Interface with the httpbis working group toensure that any CalDAV changes are consistent with good http practices.

The working group will use the following drafts as initial input for itswork: draft-daboo-icalendar-rscale-03draft-daboo-calendar-availability-05draft-daboo-icalendar-extensions-08

The following are out of scope for the working group:

- Any change that impacts backwards compatibility with existingdeployed iCalendar/iTIP/CalDAV clients and servers will be discussedby the working group with a view to minimizing disruption to deployedimplementations without compromising desirable new function.